One of the main problems linked to the management of the radio spectrum lies in the interferences that the transmission systems of a mobile network generate on the receiving systems of another broadcast network or of another mobile network. These interferences reduce the range and/or the quality of the transmissions.
The prior art known to the applicant consists, for example, in managing the spectrum statically, by conducting upstream studies of compatibility that make it possible to determine the conditions of use of these systems. The role of the international telecommunication union, or ITU, and of the CEPT (European Conference of Postal and Telecommunications Administrations) at the European level is to manage this coexistence. The coexistence is generally ensured by defining a transmission mask for each of the systems, and by adding thereto a guard band that makes it possible to consider the adjacent systems as isolated on the wireless plane. The problem resulting from this approach is two-fold: the spectrum is shared only statically and the guard band is generally significant.
Numerous studies are conducted on cognitive radio in general, the aim of which is to scan the wireless environment and exploit this information to use the spectrum that is left vacant. The main problem with this approach stems from the fact that the adjacent systems do not know one another, a priori, and that the spectrum access priority rules are generally not defined, unless a licence agreement, called LSA (licence scheme agreement), between a main user and a secondary user is defined. This agreement is specific between two users who use manual management to allocate the spectrum.
Another approach lies in the LTE technology (standardized by the Long Term Evolution 3GPP) known from the technical domain which has introduced a semi-static spectrum sharing technique between adjacent base stations. The spectrum allocation, or “load sharing”, protocol is transported by an IP internet network, to which the base stations are connected. Each operator defines the rules for sharing the spectrum that it wants to use. In particular, the LTE offers the possibility of creating a broadcast sub-network over a predetermined set of geographic areas. This sub-network shares the spectrum and the physical layer with the point-to-point or unicast transmissions, over all the base stations of a geographic area. In the context of this technology, the semi-static spectrum sharing takes place only within a single system for which the spectrum access priority rules are identical. The broadcast sub-network uses the same transmission standard and the same equipment as the LTE.
Hereinafter in the description, the expression “constrained system” will denote a system for which the frequency band is fixed, and “a non-constrained system” denotes a system for which the frequency band is flexible, in width and/or in position in the spectrum, without needing to switch it off. The LTE technology particularly addresses this criterion.
In practice, such a system is commonly implemented by using an orthogonal sub-carrier modulation, but this type of implementation is not obligatory. The expression “adjacent” corresponds to an adjacency in the spectral sense of two systems having a common radio coverage area.
The term channelization is here synonymous with radio channel width. For a given radio system, the channelization is defined by the quantity of spectrum necessary for the transmission and includes necessary guard bands that make it possible to avoid interference with the adjacent systems. In the LTE system, the channelization is quantized and adopts a value from the set {1.4 MHz, 3 MHz, 5 MHz, 10 MHz, 15 MHz, 20 MHz}. The LTE system can be positioned in different frequency bands, typically the civil mobile communication bands allocated by the ITU, but can also be deployed in other bands defined by each band-owner state or official organization (e.g. NATO).